<Lithium Ion Secondary Battery>
Since a lithium ion secondary battery is lightweight and of a high capacity in comparison with a nickel-cadmium battery and a nickel metal hydride battery, it has been put to practical use, for example, as a power supply for driving portable electronic devices such as mobile telephones, notebook-sized personal computer, video camcorders and the like, and has accomplishes rapid growth. In addition to these applications, the lithium ion secondary battery has been recently also expected as a secondary battery to replace a nickel-cadmium battery and a nickel metal hydride battery or a lead storage battery used for a power supply of battery vehicles and hybrid type battery vehicles due to the characteristics that the lithium ion secondary battery is lightweight of a high capacity.
Representative electrode materials of the lithium ion secondary battery are graphite and non-graphitizable carbon materials.
The material currently used for the electrode of the lithium ion secondary battery is graphite. One of the characteristics of graphite is that it has a relatively high theoretical charge/discharge capacity as high as 372 mAh/g. However, this is also a problem that charge/discharge capacity exceeding this value cannot be obtained, which becomes an obstacle in attaining higher capacity. In addition to this, the lithium ion secondary battery comprising an electrode made from graphite has a problem that it has poor high rate characteristics and therefore it cannot be used for as a power supply of the hybrid type battery vehicles and battery vehicles. Therefore the present condition is that new materials are being developed as electrode materials of the lithium ion secondary battery (for example, see Patent Document 1).
In the meantime, non-graphitizable carbon materials have problems that they have low capacity and insufficient high rate characteristics (for example, see Patent Document 2).
Other than these, amorphous carbon materials have been studied, but they have problems that the cycle characteristics thereof are poor and the storage stability thereof is low (for example, see Patent Documents 3, 4 and 5). In addition, artificial graphite, non-graphitizable carbon materials, carbon fibers and mesophase microspheres are being been studied. These materials have problem that the production processes including production of the starting materials, carbonization and postprocessing are complicated and require significant resources and energy consumption, and therefore the production cost is high (for example, see Patent Document 6).
<Electric Double Layer Capacitor>
An electric double layer capacitor has characteristics which cannot be provided by batteries such as capability of being rapidly charged/discharged, endurance against over-charge/discharge, longer life since it does not involve chemical reactions, applicability in a wide range of temperature and eco-friendliness due to the absence of heavy metals. The electric double layer capacitor has been used for memory back-up power supplies conventionally. In late years, the electric double layer capacitor, having marked a drastically advanced progress in higher capacitance and a development of use for high-performance energy devices, are also studied in the applications to the power storage system in combination with a solar battery and/or a fuel cell as well as in the use for engine assisting means in hybrid vehicles.
Conventional electric double layer capacitors are excellent in the power density but, on the other hand, disadvantageous in that the energy density is inferior. In the application for energy devices, capacitors having a larger capacitance have been investigated. For increasing the capacitance of an electric double layer capacitor, use of activated carbon having a large specific surface area as an electrode material has been studied to increase the capacitance of electric double layer capacitors.
The activated carbon is produced by carbonizing carbon sources derived from coal/petroleum raw materials such as cokes and pitch, carbon sources derived from synthesized polymers such as phenolic resins or carbon sources derived from plants followed by activation treatment.
Therefore, the production process itself of the activated carbon requires steps for increasing the specific surface area such as alkali activation, steam activation or combinations of these steps. In addition, methods for increasing the specific surface area have been studied as methods for improving the capacitance in itself of the electric double layer capacitors. However, it is pointed out that improvement of the capacitor capacitance by simply increasing the surface area of the activated carbon has already reached the limit (for example, see Non-Patent Document 1). In addition, since the apparent density decreases with the increase in the specific surface area of the activated carbon, capacitance per unit volume of the electric double layer capacitor decreases and such as approach is disadvantageous practically.
On this account, a method of using a carbon material in which nitrogen, a different kind of element, is incorporated into carbon as an electrode of the electric double layer capacitor has been studied as an attempt for further increasing the capacitance of the electric double layer capacitor.
In Patent Document 7, use of a nitrogen-containing carbon material produced by carbonizing a mixture of a nitrogen-containing thermosetting resin and a carbon precursor which does not contain nitrogen is studied for the electrode of the electric double layer capacitor.
In Patent Document 8, use of a nitrogen-containing carbon material produced by heat-treating a nitrogen-containing heteroaromatic compound is studied for the electrode of the electric double layer capacitor.
In Patent Document 9, use of a nitrogen-containing carbon material produced by electrolytic reduction of polytetrafluoroethylene in a solution containing a quaternary ammonium salt is studied for the electrode of the electric double layer capacitor.
In Patent Document 10, use of a nitrogen-containing carbon material produced by synthesizing and carbonizing a melamine resin or use of a nitrogen-containing carbon material produced by compositing and carbonizing a melamine resin and a swelling fluorine mica to produce a nitrogen-containing carbon material followed by treating the same with hydrofluoric acid is studied for the electrode of the electric double layer capacitor.
In Patent Document 11, use of a nitrogen-containing carbon material produced by introducing an organic compound into the inside of the zeolite pores, heating the organic compound so that the organic compound may be polymerized followed by heating and carbonizing the resultant compound, subsequently introducing gaseous nitrogen atom-containing compound to deposit nitrogen and then performing carbonization, and finally dissolving and removing the zeolite is studied for the electrode of the electric double layer capacitor.
These nitrogen-containing carbon materials obtained by the above methods has a problem that too little nitrogen is contained or alternatively hydrogen content is too high even though much nitrogen is contained.
<Fuel Cell>
The fuel cell converts chemical energy of a fuel directly to electric energy by electrochemically oxidizing the fuel such as hydrogen and methanol in a cell. Therefore, the fuel cell has a high energy conversion efficiency. In addition, since there is no generation of NOx, SOx and the like by the combustion of the fuel as in thermal power generation, the fuel cell is a clean supply source of electric energy.
Among these, a solid polymer fuel cell was developed as a power supply for spaceships since small and lightweight ones can be attained. The solid polymer fuel cell is studied as a home use for an electric supply system for fuel cell vehicles and immobilized heat and electricity supplying system, recently.
The electrode of the solid polymer fuel cell is generally constituted as a catalyst in which an active metal is dispersed on a support. Carbon materials are used for a support. The reason why carbon materials are used for a support is that conductivity is demanded besides a role as a support. Platinum and platinum alloys are common for the active metal. A supported catalyst is one in which such an active metal is highly dispersed on a support.
Conventionally, improvement of the supported catalyst has been attempted by dispersing platinum which is an active metal as finely as possible to improve the performance of the catalyst and many efforts have been particularly devoted in searching for another active metal to replace platinum which is expensive.
Under the circumstances, development aiming at enhancing the performance of the catalyst with a carbon material in which a heteroelement such as nitrogen was doped attracts attention recently.
It has been reported that oxygen reduction activity of the catalyst comprising a carbon material is improved with a nitrogen-containing carbon material. It has been reported that the high activity is thereby obtained without carrying a noble metal such as expensive platinum, or alternatively, with a slight amount of a noble metal. In addition, it has been also reported that the highly dispersed condition can be maintained by preventing the catalyst metal particles from aggregating or becoming rough particles during the production and the use of the supported catalyst (for example, see Patent Documents 12 to 17).
Patent Document 1: Japanese Patent Application Laid-Open No. 2006-164570
Patent Document 2: Japanese Patent Application Laid-Open No. 2006-140138
Patent Document 3: Japanese Patent Application Laid-Open No. 8-298111
Patent Document 4: Japanese Patent Application Laid-Open No. 2004-349217
Patent Document 5: Japanese Patent Application Laid-Open No. 2005-232291
A Patent Document 6: Japanese Patent Application Laid-Open No. 2005-44775
Patent Document 7: Japanese Patent Application Laid-Open No. 2000-1306
Patent Document 8: Japanese Patent Application Laid-Open No. 2003-137524
Patent Document 9: Japanese Patent Application Laid-Open No. 2003-247091
Patent Document 10: Japanese Patent Application Laid-Open No. 2005-239456
Patent Document 11: Japanese Patent Application Laid-Open No. 2006-310514
Patent Document 12: Japanese Patent Application Laid-Open No. 2004-79244
Patent Document 13: Japanese Patent Application Laid-Open No. 2004-207228
Patent Document 14: Japanese Patent Application Laid-Open No. 2004-330181
Patent Document 15: WO 2004/112,174/pamphlet
Patent Document 16: Japanese Patent Application Laid-Open No. 2006-331689
Patent Document 17: Japanese Patent Application Laid-Open No. 2007-26746
Non-Patent Document 1: State-of-the-art of the ubiquitous energy, p. 102, (CMC Publication (2006))